Yak-milk-derived exosomes promote proliferation of intestinal epithelial cells in an hypoxic environment

摘要

Intestinal epithelial cells (IEC) are an importantpart of the intestinal barrier. Barrier function wasdisrupted under hypoxia, but milk-derived exosomescan regulate the intestinal barrier function. However,the mechanisms underlying the association betweenyak milk exosomes and hypoxia in IEC remain poorlyunderstood. In this follow-up study, we proposed aneffective optimization method for purifying yak-milkderivedexosomes. The Western blot analyses indicatedthat the expression of the proteins of the endosomalsorting complexes required for transport (TSG101),proteins of the tetraspanin family (CD63), and heatshock protein 70 (Hsp-70) proteins from yak-milkderivedexosomes were significantly higher than thosein cow-milk-derived exosomes. Flow cytometry analysisshowed that yak milk had 3.7 times the number of exosomescompared with cow milk. Moreover, we exploredwhether yak milk exosomes could facilitate intestinalcell survival under hypoxic conditions in vitro. The3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazoliumbromide results showed that yak-milk-derived exosomessignificantly increased survival of IEC-6 cells with ratesof up to 29% for cells incubated in hypoxic conditionsfor 12 h, compared with those of cow-milk-derivedexosomes posttreatment (rates of up to 22% for cellsincubated in hypoxic conditions for 12 h). Confocalmicroscopy revealed that the IEC-6 cells uptake moreyak-milk-derived exosomes than cow milk in hypoxicconditions. Furthermore, the Western blot analysesindicated that yak-milk-derived exosomes significantlypromote oxygen-sensitive prolyl hydroxylase (PHD)-1expression and decrease the expression of hypoxiainduciblefactor-α and its downstream target vascularendothelial growth factor (VEGF) in the IEC-6 cells.Further, yak-milk-derived exosomes significantly inhibitedp53 levels. In conclusion, our findings demonstratethat yak-milk-derived exosomes more effectively activatethe hypoxia-inducible factor signaling pathway,thus promoting IEC-6 cell survival, which may resultin higher hypoxia tolerance than cow-milk-derived exosomes.